The part of the turning machine is referred to as the machine bed which for the purpose of supporting the tool and workpiece drives is designed in a sufficiently rigid manner and which to a great extent prevents the occurrence of vibrations between the different bearings. The machine bed is thus made of relatively solid material such as cast iron, granite or polymer concrete, and accordingly comprises a high degree of wall thickness. The solidity of the material used in connection with sufficiently high wall thicknesses guarantee on the one hand a sufficiently high degree of rigidity, which restricts a vibration introduction or vibration amplitude. On the other, in connection with the existing mass, the largest possible suppression of the vibration is achieved. The vibrations which are introduced are thus absorbed down to a minimum. The machine bed is, as far as possible, designed as a single part, since each division forms a weak point. Parts which provided only a low level of support to the rigidity can be designed as add-on parts. Machine bed parts which are of relevance to rigidity and strength usually comprise a wall thickness of over 7 mm. Exceptions can be add-on parts made of aluminium, which due to the production frequency comprise greater wall thicknesses. When polymer concrete is used in particular, wall thicknesses of at least 15 mm are usually necessary for machine bed parts which are of relevance to rigidity.
The machine bed can be supported on a machine frame via cushioning bearings, in such a manner that it is de-coupled from the vibrations. In this case, the machine frame fulfils a transportation, table and support function for the machine bed, as well as an installation space function for add-on parts. The machine frame rests via mounting feet on a bearing or floor area. The support plane is ideally tensioned by the mounting feet or their mounting surface. The fact that the mounting surfaces do not lie precisely on one plane due to the alignment according to a floor surface is here not taken into account. The machine frame can in relation to the vertical structure also be designed in two or more parts. Generally, it can be provided that the machine bed is supported via cushioning bearings directly on a floor surface. This depends on the height of the machine bed or the height of the floor or platform surface, which then fulfils the machine frame function.
The space in which the direct flight of chips can be anticipated is referred to as the chip space. Starting from the working space, i.e. the space in which the movement of the tool or workpiece can be anticipated, the chip space is wider or larger, and ends at the respective wall against which the chips impact and flow with the coolant or lubricant. Walls of this type are usually raised in relation to the horizontal plane, so that a run-off of the coolant and lubricant together with the chips to an outflow opening of the chip space is guaranteed. In the area of the outlet opening, the different coolant and lubricant flows run together and leave the chip space. A coolant and lubricant channel is connected to the outlet opening, which guides the coolant and lubricant flow downwards and then deflects it towards one side.
The term “linear motor” comprises the class of asynchronous motors, in particular the class of synchronous motors both in the flat design as well as in the variant as plunger coil or voice-coil drive.
A turning machine for machining optical workpieces is already known from DE 10 2005 021 638 B4. The turning machine comprises a fast tool arrangement and a workpiece spindle arrangement, which is supported on a rigid machine bed lower part and is covered by a machine upper part. The machine bed lower part and the machine upper part are formed as a single part made of polymer concrete. The machine bed lower part fulfils the function of the machine frame. The machine bed overall restricts a chip space downwards and to the side, wherein the chip space comprises a run-off opening in the area of a floor wall, to which a coolant and lubricant channel is connected. Due to the coolant and lubricant channel, the medium to be removed is removed collectively from the chip space and then deflected towards the side.
With turning machines for synthetic spectacle lenses, the use of a highly dynamic turning tool which oscillates at between 50 Hz and 200 Hz is necessary in order to achieve the highest possible workpiece rotation speed and thus the lowest possible machining time. In this manner, a sufficient high cutting speed of the turning process is also achieved. As a rule, linear motors are used as a drive for the tool, with the turning tool directly affixed to their actuator. Thus, a direct implementation of the actuator or motor movement is guaranteed without the use of gear members.
The linear motors, which can be used for a sufficiently high frequency oscillation movement, must however comprise sufficiently large primary and secondary components in order to be able to generate the necessary acceleration forces. However, the size of the primary and secondary components entails a relatively high weight. In order to make the accelerating actuator as light as possible, it is designed without iron, and advantageously comprises a light synthetic core with windings arranged on it. The actuator is the primary component in the case of the synchronous motor, which must be moved such that it oscillates at a high frequency.
When producing spectacle lenses, very high precision is required, in order that the spectacle lens surface being produced while rotating requires the shortest possible subsequent polishing, or no subsequent polishing at all. The turning tool or its drive constantly induce vibrations into the machine bed due to the high frequency oscillation movement, which have a negative effect on the precision of the cutting or turning process of the spectacle lens surface.
In order that the required high precision can be guaranteed, the machine bed must on the one hand be designed with sufficient rigidity, particularly in relation to the oscillation movement between both bearing surfaces and taking into account the dynamic load connected with it. On the other hand, it is necessary to design the mass of the machine bed as large as possible, so that the vibrations introduced by the turning tool are suppressed as comprehensively as possible. This is also the case according to the principle of DE 10 2005 021 638 B4, where the upper part of the machine is formed of polymer concrete and is coupled as a single part with the machine part.
The mass used entails a corresponding weight on the one hand, and on the other, a corresponding constructional size of the turning machine.
The deformations which occur at the contact point between the tool and the workpiece as a result of the machining forces consist of the deformations of all components and machine bed elements involved in the force transfer. With a force flow and deformation analysis, the load of the individual components and machine bed elements and the respective portion of the overall deformations between the force contact points are examined. Due to the differently sized lever arms, the forces on the respective force contact point generate different moments in different directions, which cause a corresponding deformation of the machine bed.
With the structural design of the machine bed profiles, account should be taken of both the flexural load and the torsion load. Thus, the flexural strength depends mainly on the equatorial moment of inertia and the torsion strength depends primarily on the polar moment of inertia. Accordingly, persons skilled in the art attempt to achieve both large masses and close and large machine bed profiles with tool machines, in order to achieve maximum stability. Thus, all loads are taken into account. Materials with a high degree of vibration cushioning are sought which additionally provide a large machine bed mass, so that the machine bed is not excessively excited by vibrations.